Plasma enhanced chemical vapor deposition tools include a reaction chamber having a susceptor upon which one or more semiconductor substrate(s) lie during a plasma deposition of material over the substrate(s). Unfortunately, not all of the depositing material forms on the wafer. Some of it, as well as reaction byproducts, deposits on internal surfaces of the reaction chamber. This includes the sidewalls and other components therein, such as gas injectors and heaters. Further, depending on the chemistry utilized, some of the undesired deposited material on the reactor components can be dislodged in subsequent depositions and end up as contaminants deposited on the substrates.
One particular process where such is problematic involves the plasma enhanced chemical vapor deposition of thin titanium films utilizing TiCl.sub.4 and H.sub.2 as reactive precursors. Reaction byproducts from the deposition get deposited on internal chamber sidewalls and other components. These byproducts can be dislodged in subsequent depositions, and deposit on the substrates which can result in incredible yield loss of dies on the substrates being processed.
The present accepted technique to largely prevent this from occurring utilizes a Cl.sub.2 plasma clean of the internal reactor components between each separate plasma depositing step. Many plasma reactor susceptors are, however, made of a material which is corrosive to attack by a chlorine containing plasma, particularly at elevated temperatures. Aluminum nitride is one example such susceptor material. Accordingly, during the chlorine plasma cleans, the susceptor is covered with a suitable and ultimately discardable protector typically in the shape of a conventional wafer which the tool is designed to process. Accordingly at the conclusion of a plasma deposition, the processed substrate is removed from the chamber, and a dummy protectable plate placed over the susceptor. Plasma cleaning with the chlorine gas then occurs, followed by removal of the dummy protector and placement of another semiconductor substrate upon the susceptor for processing. This, of course, significantly adversely affects throughput because of all the separate cleanings and required robotic placement of dummy plates over the susceptor during the plasma cleanings. Conducting such plasma cleanings every second, third or more depositings has been attempted, but with less than satisfactory results. Considerable yield loss occurs, and/or process uniformity from wafer to wafer between cleanings is significantly adversely affected.
Accordingly, it would be desirable to develop improved processes which better contend with material which deposits on internal chamber surfaces during plasma depositions on semiconductor substrates.